(349g) Geometric Frustration-Induced Phase Behavior in Spherically Symmetric Colloids

Brownian particles interacting with hard-sphere potential are considered as ‘fruit flies’ in the field of condensed matter physics and are widely used to study the fundamentals underlying the phase behavior and flow mechanics of particulate suspensions. Our work probes the interesting dynamics and associated phase behavior created by surface anisotropy in Brownian systems. We synthesize polymethylmethacrylate (PMMA) microspheres with varying surface roughness through free-radical dispersion polymerization, maintaining spherical symmetry, to understand the effect of geometric frustration created by the surface bumps. We use confocal laser scanning microscopy to image suspensions at various ϕ and extract particle positions using conventional image-processing algorithms. We report a method to extract the contact at jamming point (ϕ_J) by extrapolating the average transient neighbors, <z>, in suspensions approaching jamming. We define the contact distance by considering the length scale contributions from particle roughness, polydispersity and steric brushes on the particle surface. Initial data shows that the contact scaling shows the form Δz ~ (Δϕ)^α_, where Δz = <z> - z_Jand Δϕ = ϕ - ϕ_J, and the exponent α is function of the surface bumpiness. We hypothesize that connecting contact scaling below ϕ_Jto the mean-squared displacement (MSD) at the respective Δϕ will help us understand the rich phase behavior of similar anisotropic materials found in nature, ranging from biomolecular assemblies to industrial particulates.